******DID YOU NOT RECEIVE THIS EMAIL? SEND ME AN EMAIL ABOUT IT THEN***** Date: Mon, 03 Feb 2003 2:30 PM From: Mark Jacobson To: 810-023-01@uni.edu Subject: Attenuation and repeaters... Hi 023 students, Here are some definitions reviewing today's class. The definitions are found from the link: http://www.cisco.com/univercd/cc/td/doc/cisintwk/ita/index.htm which is linked to from our class web page via the hypertext words: Networking terms and concepts - This LAN is your LAN ---------------------------------------------------- Our class web page is URL: http://www.cns.uni.edu/~jacobson/c023.html attenuation Loss of communication signal energy. (see textbook glossary page 899 - much better definition there!). A signal's loss of strength as it travels farther from its source. What is the source of the signal? How does a signal travel? repeater Device that regenerates and propagates electrical signals between two network segments. See also segment. bridge Device that connects and passes packets between two network segments that use the same communications protocol. Bridges operate at the data link layer (Layer 2) of the OSI reference model. In general, a bridge filters, forwards, or floods an incoming frame based on the MAC address of that frame. segment 1. Section of a network that is bounded by bridges, routers, or switches. 2. In a LAN using a bus topology, a segment is a continuous electrical circuit that often is connected to other such segments with repeaters. 3. Term used in the TCP specification to describe a single transport layer unit of information. The terms datagram, frame, message, and packet also are used to describe logical information groupings at various layers of the OSI reference model and in various technology circles. The 2nd definition of segment applies to the REPEATER concept and definition given about. Segmenting a network so it is bounded by bridges between different groups of computers and devices would mean that: It 80% of the locally destined LAN traffic from marketing stays within the accounting department, and only 20% goes outside to other departments, and only 20% of all traffic generated elsewhere has its destination within the marketing department, then a bridge can be used to keep 80% of the other department's packets off of our wires and the bridge can also be used to only let the 20% of the traffic out of our department that needs to go elsewhere. The 80% that has local marketing department destination hosts, can stay here on our segment. Read chapter 6 of the textbook for more on repeaters, bridges and routers. Mark